Yet in TNG it appears the 'Prime Directive' sudenly meant no interference whatsoever in any world not a ,member of the UFP - and it was ridiculous (IMO) to hear Picard say "Well, we can't be involved in another (space faring) culture's internal affairs..." EVEN WHEN it was clear inaction on Picard's part would have a VERY detrimental effect on Star Fleet. <---- Sorry, but I thought part of Star Fleet's mission WAS Federation protection and defense - so Picard (IMO) wasn't much of a Captain or a Federation citizen in that aspect.

Taken to its logical extreme, the TNG Prime Directive should prevent Starfleet from defending itself from attack by the Klingons or another warlike race. It's a natural part of their culture to attack other people, so for Starfleet to shoot back would, y'know, interfere with that.